Microscratching and fretting of electro-co-deposited Cr-based composite coatings with BN, graphene, and diamond reinforcements

Abstract

Herein, enhanced damage tolerance of electrochemically processed Cr-based coatings reinforced with BN (Cr–BN), diamond (Cr–D) and graphene (Cr–Gr) is presented. The effect of micro-meter sized BN and diamond particles as well as 2D graphene nano-flakes in Cr matrix is studied due to its excellent mechanical properties and lubricating nature. The highest hardness of Cr–D (~ 23 GPa) is ascribed to the highest dislocation density of ~ 18×1011 cm−2, estimated through Taylor’s model. Scratch test revealed minimum wear volume and coefficient of friction of ~ 27 ± 0.47 × 10–14 m3 and 0.14, respectively, for Cr–D coating. Fretting wear results were concurrent with the scratch test, with Cr–D exhibiting minimum coefficient of friction (COF ~ 0.53) and wear loss (wear volume ~ 0.222 × 10–3 mm3). Diamond particles promote strong bonding due to mechanical interlocking, and efficient load transfer that restricts wear, and passes as a suitable reinforcement of Cr-coating for tribological applications subjected to high load and temperature conditions.